“The design of “Coming Together” is simple, even minimal: Steve ben Israel reads and rereads one of Sam Melville’s letters from Attica over a jazzy, repetitious vamp. Yet the result is political art as expressive and accessible as Guernica. In ben Israel’s interpretation, Melville’s prison years have made him both visionary and mad, and the torment of his incarceration is rendered more vivid by the nagging intensity of the music. The other side features a less inspiring political piece and a percussion composition, each likable but not compelling, but that’s a cavil. “Coming Together” is amazing. A-”